In recent years, with a trend toward a greater number of pixels of a solid-state image sensor, there are increasing demands for a zoom lens having higher image forming capability and higher zoom ratio, for a small-sized digital camera and a small sized video camera carrying a small-sized image pickup unit equipped with a solid-state image sensor such as a CCD (Charge Coupled Devices) type image sensor or a CMOS (Complementary Metal-Oxide Semiconductor) type image sensor. In addition, a zoom lens for a small-sized image pickup unit is requested to be further smaller in size.
There is provided, for example, a small-sized zoom lens for a small-sized image pickup apparatus including a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, a fifth lens group having negative refractive power, and a sixth lens group having positive or negative refractive power, and the small-sized zoom lens is provided with a prism for bending an optical path arranged in the first lens group in order to make a zoom lens to be thin in its thickness, as disclosed in TOKUKAI No. 2005-195757.
However, the disclosed zoom lens has problems that the zoom ratio is as small as about 3× though 5×, and its total length is long for its zoom ratio.